The present invention relates to a method and a device for compressing granular molding materials, in particular foundry molding materials, wherein the molding material is introduced into a molding device comprising a pattern plate having pattern arranged thereon, and a filling and molding frame.
The compression of granular molding materials for the purposes of manufacturing foundry and sand moldings is known from various methods such as those described in U.S. Pat. Nos. 4,415,015 and 4,828,007 which are assigned to the assignee of the instant invention.
It is known to distribute molding material either (1) loose over a pattern arranged in the molding box on the pattern plate and then subsequently compressing it (mechanically or by means of a compressed air surge) or (2) shooting the molding material from a supply container directly into the molding box.
It has been shown however, that neither of these methods guarantee optimum results. Difficulties arise particularly with regard to the homogeneity of the compressed molding material.
With gas pressure methods in which the compression process occurs by means of a gas pressure, wherein either a gas mixture is led by ignition to an exothermic reaction, or a highly compressed pressure gas which is released for a short time, the molding device is filled with molding sand from a sand container with a predetermined quantity of molding sand. The sand container is driven over the molding device and swung away after emptying the container of sand. Subsequently a compressing unit is positioned over the molding device and the pressure surge triggered.
These method stages, the swinging to and fro of the sand container on the one hand and the pressure unit on the other hand are detrimental to cycle time. The demand for economical manufacturing requires shorter cycle times.
Accordingly, it is the principal object of the present invention to improve the know methods so that evenly compressed moldings with reproducibility and great hardness can be manufactured in the shortest cycle times possible in an economic manner.